1. Field of the Invention
The present invention relates generally to the field of sensors for beam imaging and, in particular, to a new and useful beam imaging sensor for use in determining, for example, the power density distribution of a beam including, but not limited to, an electron beam or an ion beam. In one embodiment, the beam imaging sensor of the present invention comprises, among other items, a circumferential slit that is either circular, elliptical or polygonal in nature. In another embodiment, the beam imaging sensor of the present invention comprises, among other things, a discontinuous partially circumferential slit. Also disclosed is a method for using the various beams sensor embodiments of the present invention.
2. Description of the Related Art
Electron beams are considered to be the most precise and clean method available for welding thick sections of materials. Unfortunately, electron beams suffer one critical deficiency, namely the repeatability of focusing the beam to a known power density. Without the ability to reliably reproduce the power distribution in an electron beam, weld quality cannot be guaranteed. This problem is exacerbated by the fact the many welds are made over a period of time and with different welding operators. Further complications arise when welds are developed on one machine than transferred to a different machine for production. Various electron beam diagnostic methods have been developed that, at some level, enable the characterization of the power density distribution in high power electron beams. Such diagnostic methods are exemplified by U.S. Pat. Nos. 5,382,895; 5,468,966; 5,554,926; 5,583,427; 6,300,755; 7,288,772; 7,348,568; 7,378,830; and 7,902,503. However, the methods and sensors disclosed therein all suffer from a number of drawbacks. While not wishing to be bound to any one drawback, some, if not all, of the prior art sensors suffer from thermal load drawbacks that cause the sensors of the prior art to fail at lower energy levels (e.g., 5 kW).
Given the above, a need exists for a beam imaging sensor that provides superior functionality and accuracy while still being able to withstand beam energy settings in excess of 5 kW.